We propose to compile and make available data on mortality surfaces over age and time for the United States, for regional and black and white sub-populations knot the United States, for East and West Germany and for 15 other countries. Furthermore, we will develop and test innovative demographic methods for modeling mortality surfaces. The data and methods will be useful to many researchers interested in analyzing questions concerning mortality dynamics and comparisons. We will illustrate this by using the data and methods for modeling mortality surfaces. These data and methods will be useful to many researchers interested in analyzing questions concerning mortality dynamics and comparisons. We will illustrate this by using the data and methods to shed light on two demographic puzzles, one concerning the United States and the other concerning Germany. Although death rates in the U.s. are high before age 65, after this age and especially after age 80 people in the United States survive longer than people in Western Europe and Japan. Many factors may contribute to the U.S. advantage; we propose to study three. In particular, we will use mortality-surface data and methods to analyze they hypothesis that health immigrants contribute to the mortality advantage. We will test whether high death rates as younger ages may lower death rates at older ages. Finally, and perhaps most importantly, we will analyze the hypothesis that the Medicare system lowers U.s. mortality at older ages. The German puzzle pertains to the effects of reunification in 1990. Death rates in East Germany fell so rapidly after 1990 that much of the West Germany mortality advantage was eliminated. Improvements were particularly dramatic at oldest-old ages. The narrowing of the mortality gap between East and West Germany began, however, several years before reunification. Hence it is not clear how much the effects of reunification vs. the effects of other factors account for the change: we will use mortality-surface data and methods to analyze this question.